Transcript Hypothesis testing simplified

Hypothesis testing simplified
Objective: Describe a variable
- Mean, Median, Mode, Standard Deviation
• Examples:
• What is the percentage of totally satisfied
customers in our database?
• What is the most common income in our data
base?
Objective: compare one group to a
hypothetical/ set value
• Z-test (rare) or T-test (one sample t-test; very
often)
• Good with interval and ratio data
• Examples:
– Santa Fe grill wants to check whether the prices
they have are perceived as reasonable or not?
– I am doing a better job at satisfying customers
than average?
What does it mean?
P-value and alpha-level
• The P-value (probability value) is a measure of
how confident we can be that what we observe in
the sample is also true for the population.
• How confident we want to be?
• 90%?
• 95%?
• 100?
• The alpha level is the P-value that we as
researchers decide to accept before we will be
confident enough to release a finding.
Statistical test of significance
• a result is called statistically significant if it is
unlikely to have occurred by chance.
Objective: Compare two unpaired
groups
• Unpaired t-test (independent samples t-test)
• Example:
– Is the satisfaction level of women different than
the satisfaction level of men?
Comparing Two Means with Independent
Samples t-Test
Objective: comparing two paired
groups
• The Paired Samples T-Test compares the
means of two variables. It computes the
difference between the two variables for each
case, and tests to see if the average difference
is significantly different from zero.
Satisfaction
pre-recovery
Satisfaction
Difference
post-recovery
3
5
2
3
3
0
1
5
4
4
4
0